<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="https://cdn.jsdelivr.net/npm/vue@2/dist/vue.js"></script>
    <style>
        p{
            background-color: red;
        }
      .v-leave-to{
          opacity: 0;;
          transform: scale(0);
      }
      .v-leave-active{
          transition: all 5s;
      }
    </style>
</head>

<body>
    <div id="app">
        <button @click="show=!show">切换</button>
        <transition>
            <p v-if="show">显示</p>
        </transition>
    </div>
    <script>
        var app = new Vue({
            el: "#app",
            data: {
                show: true,
            }
        })
    </script>
</body>

</html>